Analog and electronic circuits

In the step response of an RC circuit, how long does it take for the capacitor voltage to reach about 63% of its final value?

  1. ARC / 2
  2. BRC (the time constant)
  3. C5RC
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Answer: B. RC (the time constant)

The capacitor voltage in an RC circuit changes as V(1 − e^(−t/RC)) and reaches about 63% of its final value at t = RC. This RC is called the time constant τ. After about 5τ, it exceeds 99% of the final value.

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